The contact receptacles for functional testing of FPBGA packages often have, for electrical conduct-connection, spring pins (pogo pins) or micro-spring contacts that are used for the contact-connection of the contact terminals in the form of solder ball contact arrays of the FPBGA packages. In this case, the contacts are arranged in the grid pitch precisely like the solder balls of the micro-ball contact array.
However, these contacts are not sufficient to meet the future requirements made of test receptacles. In particular, consideration is given to unresolved problems such as the non-lossless energy transmission by virtue of existing discontinuities and also the contamination of the test systems by extremely fine abrasion on all the sliding parts of the test system.
The limiting frequency is 1 GHz, for example, in the case of the spring pins having a length of approximately 5 mm that are customarily used. This is due to the dynamic internal resistances of the contact system.
Furthermore, the test receptacles are subjected to high thermal loading due to the continual miniaturization of the integrated circuits and the associated poorer heat dissipation. The consequence of this is that both the contact element and the solder ball are subjected to severe thermal loading and thus corrode rapidly.
Moreover, the continual reduction of the connecting pitch leads to a non-linear rise in the signal crosstalk, which cannot be avoided with known technical solutions, such as with spring pins, for example.
Owing to the reasons mentioned above, it is necessary to develop cost-effective test receptacles that are both mechanically highly stable, insensitive to thermal effects and solve the problem of crosstalk in the case of small connecting pitches. In this case, the contact elements must have good self-cleaning capacities and additionally be able to reliably penetrate a substrate situated on the contact balls.